1. Field of Invention
The invention relates to a clamping device for clamping a vehicle wheel onto a shaft of a wheel balancing machine, with a clamping flange and with a plurality of centering bolts, wherein the clamping flange has a plurality of recesses for receiving the centering bolts, and wherein each centering bolt can be inserted releasably by means of an insertion region into a recess. Furthermore, the present invention relates to a clamping flange and a centering bolt, each designed for use in a clamping device of the abovementioned type.
2. Description of Related Art
A clamping device of the abovementioned type is known, for example, from European Patent Application EP 0 738 885 A2 and corresponding U.S. Pat. No. 5,665,911 and serves to clamp wheels of different types of motor vehicles onto a shaft of a wheel balancing machine. The known clamping device has a central guide bore in the clamping flange for axially guiding the clamping flange on the shaft of the wheel balancing machine and is provided with at least two groups, arranged in the clamping flange, of axially parallel centering bores which are arranged on various circles of different diameter and/or in a different number and at the same circumferential distance. In this case, the arrangements of holes correspond to the arrangement of holes in the rims of wheels of different types of motor vehicles. In addition, the known clamping device has centering bolts which can be inserted into the centering bores of the clamping flange and at the free ends of which centering cones are provided.
In order to clamp a vehicle wheel onto the shaft of the wheel balancing machine, the centering bolts are, first of all, inserted into a group of bores in the clamping flange, the arrangement of the bores corresponding to the arrangement of holes in the rim of a wheel to be clamped. The wheel is then pushed with the rim onto the shaft of the wheel balancing machine until the rim bears against a stop part mounted on the shaft. In the process, the stop part engages in the central hole in the rim of the wheel to be clamped. The clamping flange is then pushed by the central guide bore onto the shaft of the wheel balancing machine until the centering cones of the centering bolts engage in the fastening holes in the rim of the wheel. A clamping nut is subsequently screwed onto a thread provided on the shaft of the wheel balancing machine until the rear side of the rim comes to bear against a bearing flange of the shaft of the wheel balancing machine. The rim is oriented as a result in a plane perpendicular to the axis of the wheel balancing machine. The centering cones of the centering bolts, which centering cones engage in the centering holes of the rim, bring about a radial centering, with the clamping flange contributing to preventing the occurrence of a dynamic unbalance during the wheel balancing operation.
In order to clamp a different type of vehicle wheel, the centering bolts have to be pulled out of the centering bores in the clamping flange and inserted into a different group of centering bores in the clamping flange, the arrangement of which centering bores corresponds to the arrangement of centering holes in the rim of the new type of wheel. The centering bolts and the corresponding bores in the clamping flange have to be manufactured with a high degree of precision in order to ensure, in a substantially play-free manner, a satisfactory installation of the vehicle wheels which are to be balanced.
In order to secure the centering bolts on the clamping flange from falling out, which can be attributed in particular to the wear of the bolt holders during a progressive period of use of the known clamping device, the ends of the centering bolts on the side of the insertion region generally have a rubber ring which, after the bolt end has been inserted through the centering bore, expands on the rear side of the clamping flange and therefore prevents the bolt from falling out. This manner of fixing the centering bolts on the clamping flange ensures a sufficient holding force of the bolts on the clamping flange. A disadvantage in this case is that some of the centering bolts can only be inserted into the centering bores with a considerable amount of effort. It has to be ensured that each centering bolt emerges at its end having the rubber ring on the rear side of the clamping flange such that the rubber ring can expand. In order to pull the bolt out, it then has to be pulled out of the bore counter to the holding force of the rubber ring, which in turn requires a corresponding amount of effort. If the bolts are not moved for a relatively long period of time, the centering bolts may furthermore become stuck in the centering bores, which results in an increased effort being needed to pull the bolts out of the centering bores.
Furthermore, a clamping device of the type mentioned at the beginning is known from German Patent Application DE 103 31 129 A1 and corresponding U.S. Pat. No. 7,010,975 B2. In this known clamping device, centering bolts are likewise provided, said bolts being fixed releasably in a group of recesses in a clamping flange corresponding to the arrangement of holes in a rim of a wheel to be clamped onto a shaft of a wheel balancing machine. In order to reduce centering errors and/or unbalance errors due to play between the centering bolts and the clamping flange, for example due to manufacturing tolerances or wear, the centering bolt has an elastically deformable circumference which, in a functional position, bears against a wall surface of the clamping flange, the wall surface bounding the recess. The circumference can be deformed both hydraulically and mechanically. This creates the possibility of compensating for the play between the centering bolt and the clamping flange due to manufacturing tolerances and inaccuracies during the production of the centering bolts and of the recesses in the clamping flange and of therefore reducing centering errors during the clamping operation and of wheel balancing errors during the balancing of the vehicle wheel. Wear to the bolt or to the clamping flange that results from use can also be compensated for by readjusting or adapting the circumference of the centering bolt to the associated recess in the clamping flange. A securing ring also prevents the release here of the bolt from the clamping flange, which results in the above-described disadvantages. Furthermore, the deformation of the circumference of the centering bolt is structurally complicated and associated with high production costs. The insertion region of the centering bolt is also drilled to be hollow, thus significantly reducing the component strength of the centering bolts.